Arcgis Geostatistical Analyst Tutorial Copyright © 2001, 2003–2006 ESRI All Rights Reserved
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ArcGIS® 9 ArcGIS Geostatistical Analyst Tutorial Copyright © 2001, 2003–2006 ESRI All Rights Reserved. Printed in the United States of America. The information contained in this document is the exclusive property of ESRI. This work is protected under United States copyright law and the copyright laws of the given countries of origin and applicable international laws, treaties, and/or conventions. No part of this work may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying or recording, or by any information storage or retrieval system, except as expressly permitted in writing by ESRI. All requests should be sent to Attention: Contracts Manager, ESRI, 380 New York Street, Redlands, CA 92373-8100, USA. The information contained in this document is subject to change without notice. DATA CREDITS Carpathian Mountains data supplied by USDA Forest Service, Riverside, California, and is used here with permission. Radioceasium data supplied by International Sakharov Environmental University, Minsk, Belarus, and is used here with permission. Copyright © 1996. Air quality data for California supplied by California Environmental Protection Agency, Air Resource Board, and is used here with permission. Copyright © 1997. Radioceasium contamination in forest berries data supplied by the Institute of Radiation Safety “BELRAD”, Minsk, Belarus, and is used here with permission. Copyright © 1996. CONTRIBUTING WRITERS Kevin Johnston, Jay M. Ver Hoef, Konstantin Krivoruchko, and Neil Lucas DATA DISCLAIMER THE DATA VENDOR(S) INCLUDED IN THIS WORK IS AN INDEPENDENT COMPANY AND, AS SUCH, ESRI MAKES NO GUARANTEES AS TO THE QUALITY, COMPLETENESS, AND/OR ACCURACY OF THE DATA. EVERY EFFORT HAS BEEN MADE TO ENSURE THE ACCURACY OF THE DATA INCLUDED IN THIS WORK, BUT THE INFORMATION IS DYNAMIC IN NATURE AND IS SUBJECT TO CHANGE WITHOUT NOTICE. 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Attribution.pmd 1 05/23/2006, 9:39 AM ArcGIS Geostatistical Analyst Tutorial IN THIS TUTORIAL With Geostatistical Analyst, you can easily create a continuous surface, or map, from measured sample points stored in a point-feature layer, raster • Exercise 1: Creating a surface layer, or by using polygon centroids. The sample points may be measurements using default parameters such as elevation, depth to the water table, or levels of pollution, as is the case • Exercise 2: Exploring your data in this tutorial. When used in conjunction with ArcMap, Geostatistical Analyst provides a comprehensive set of tools for creating surfaces that can be used • Exercise 3: Mapping ozone to visualize, analyze, and understand spatial phenomena. concentration Tutorial scenario • Exercise 4: Comparing models The U.S. Environmental Protection Agency is responsible for monitoring • Exercise 5: Mapping the atmospheric ozone concentration in California. Ozone concentration is mea- probability of ozone exceeding a sured at monitoring stations throughout the state. critical threshold The locations of the stations are shown here. The concentration levels of ozone are known for • Exercise 6: Producing the final map all of the stations, but we are also interested in knowing the level for every location in California. However, due to cost and practicality, monitoring stations cannot be everywhere. Geostatistical Analyst provides tools that make the best predic- tions possible by examining the relationships between all of the sample points and producing a continuous surface of ozone concentration, standard errors (uncertainty) of predictions, and probabilities that critical values are exceeded. 1 ch02_Tutorial.pmd 1 05/23/2006, 9:31 AM Introduction to the tutorial The data you’ll need for this tutorial is included on the using the ESDA tools and working with the geostatistical Geostatistical Analyst installation disk. The datasets were parameters, you will be able to create a more accurate provided courtesy of the California Air Resources Board. surface. The datasets are: Many times it is not the actual values of some caustic Dataset Description health risk that is of concern, but rather if it is above some toxic level. If this is the case, immediate action must be ca_outline Outline map of California taken. The third surface you create will assess the probabil- ca_ozone_pts Ozone point samples (ppm) ity that a critical ozone threshold value has been exceeded. ca_cities Location of major California cities For this tutorial, the critical threshold will be if the maximum ca_hillshade A hillshade map of California average of ozone goes above 0.12 ppm in any eight-hour period during the year; then the location should be closely The ozone dataset (ca_ozone_pts) represents the 1996 monitored. You will use Geostatistical Analyst to predict the maximum eight-hour average concentration of ozone in probability of values complying with this standard. parts per million (ppm). (The measurements were taken daily and grouped into eight-hour blocks.) The original data This tutorial is divided into individual tasks that are designed has been modified for the purposes of the tutorial and to let you explore the capabilities of Geostatistical Analyst should not be taken to be accurate data. at your own pace. To get additional help, explore the ArcMap online Help system or sennnnnne Using ArcMap. From the ozone point samples (measurements), you will produce two continuous surfaces (maps), predicting the • Exercise 1 takes you through accessing Geostatistical values of ozone concentration for every location in the State Analyst and through the process of creating a surface of of California based on the sample points that you have. The ozone concentration to show you how easy it is to create first map that you create will simply use all default options a surface using the default parameters. to show you how easy it is to create a surface from your • Exercise 2 guides you through the process of exploring sample points. The second map that you produce will allow your data before you create the surface in order to spot you to incorporate more of the spatial relationships that are outliers in the data and to recognize trends. discovered among the points. When creating this second • Exercise 3 creates the second surface that considers map, you will use the ESDA tools to examine your data. more of the spatial relationships discovered in Exercise 2 You will also be introduced to some of the geostatistical and improves on the surface you created in Exercise 1. options that you can use to create a surface such as This exercise also introduces you to some of the basic removing trends and modeling spatial autocorrelation. By concepts of geostatistics. 2 ARCGIS GEOSTATISTICAL ANALYST T UTORIAL ch02_Tutorial.pmd 2 05/23/2006, 9:31 AM • Exercise 4 shows you how to compare the results of the two surfaces that you created in Exercises 1 and 3 in order to decide which provides the better predictions of the unknown values. • Exercise 5 takes you through the process of mapping the probability that ozone exceeds a critical threshold, thus creating the third surface. • Exercise 6 shows you how to present the surfaces you created in Exercises 3 and 5 for final display, using ArcMap functionality. You will need a few hours of focused time to complete the tutorial. However, you can also perform the exercises one at a time if you wish, saving your results after each exercise. ARCGIS GEOSTATISTICAL ANALYST T UTORIAL 3 ch02_Tutorial.pmd 3 05/23/2006, 9:31 AM Exercise 1: Creating a surface using default parameters Before you begin you must first start ArcMap and enable 1 5 Geostatistical Analyst. Starting ArcMap and enabling Geostatistical 7 Analyst 4 Click the Start button on the Windows taskbar, point to Programs, point to ArcGIS, and click ArcMap. In ArcMap, click Tools, click Extensions, and check Geostatistical Analyst. Click Close. Adding the Geostatistical Analyst toolbar to ArcMap Click View, point to Toolbars, and click Geostatistical Analyst. Adding data layers to ArcMap 6 Once the data has been added, you can use ArcMap to display the data and, if necessary, to change the properties of each layer (symbology, and so on). The ca_outline layer is now displayed transparently with just the outline visible. This allows you to see the layers 1. Click the Add Data button on the Standard toolbar. that you will create in this tutorial underneath this layer. 2. Navigate to the folder where you installed the tutorial data (the default installation path is Saving your map C:\ArcGIS\ArcTutor\Geostatistics), hold down the Ctrl It is recommended that you save your map after each key, then click and highlight the ca_ozone_pts and exercise.